1. Field of the Invention
This invention relates to a method for analyzing data, and, more particularly, a method for analyzing data relating to hematology test results on aged samples of blood.
2. Discussion of the Art
Automated hematology analyzers are instruments that have been designed to completely automate the analysis of samples of blood. Typically, automated hematology analyzers are used to differentiate the individual blood cells in the samples, count the individual blood cells in the samples, and in some cases, estimate the size of the individual blood cells in the samples. The erythrocyte mean cell volume (hereinafter, alternately, “MCV”) is one of the key determinants used in the screening and classification of hematological disease. Automated hematology analyzers have the capability of accurately measuring the value of MCV as part of the blood count. The value of MCV is useful for the primary classification of various disorders of the red blood cells.
It is widely accepted that during storage of samples of blood, the erythrocyte mean cell volume will increase as a function of both time and temperature. Significant changes in the value of MCV can be observed after about 24 hours of storage at room temperature (about 70° C.). These increases can be of sufficient magnitude to result in improper classification of hematology results, thereby resulting in a problem for laboratories that are required to process aged samples of blood. Improper classification of aged samples of blood can lead to such problems as failing to perform follow-up investigations in microcytic patients whose value of MCV has been overestimated, and, consequently, reported to be normal. It is also possible for the value of MCV of a patient to be overestimated when the value of MCV is, in reality, normal, thereby generating unnecessary confirmatory, follow-up tests, which are inappropriate and potentially costly.
In contrast to the erythrocyte mean cell volume, the erythrocyte mean cell hemoglobin (hereinafter, alternately, “MCH”) is not subject to changes in the short term (e.g., over a period of several days), because hemoglobin is trapped within the erythrocytes until the cells break down, i.e., undergo hemolysis. In almost all samples of blood, this process of hemolysis does not occur to a significant extent until a number of days after the drawing of the sample.
The relationship between the value of MCV and the value of MCH is generally constant, and is preferably defined by the erythrocyte mean hemoglobin concentration (hereinafter, alternately, “MCHC”). The erythrocyte mean hemoglobin concentration is determined by dividing the erythrocyte mean cell hemoglobin by the erythrocyte mean cell volume (MCHC=MCH/MCV). Because the value of MCV increases as a function of time, the value of MCHC decreases as a function of time. The value of MCHC of a fresh sample of blood is tightly constrained, e.g., typically ranging from about 32 to about 36 g/dl. However, there is a direct correlation between the value of MCH and the value of MCHC. Accordingly, if a sample of blood has been stored and is no longer fresh, it would be desirable to estimate the value of MCV for that sample of blood when it was fresh. Consequently, it is desired to develop a method for using the values of MCH and MCHC of a stored sample of blood to calculate the value of MCV for that sample of blood when that sample of blood was fresh (i.e., before the sample was stored).
In conventional methods in hematology, samples of blood are typically refrigerated to decrease the rate at which the value of MCV increases during storage. While this approach is useful, the conditions demanded are difficult to maintain, especially during such activities as transport from remote facilities.